Answer this question truthfully
### Question: What causes Unstable angina / Non ST elevation myocardial infarction?
### Response: Coronary artery disease due to atherosclerosis is by far the most common cause of unstable angina. Atherosclerosis is the buildup of fatty material called plaque along the walls of the arteries. This causes arteries to become less flexible and narrow, which interrupts blood flow to the heart, causing chest pain.
At first, angina may be considered stable. The chest pain only occurs with activity or stress. The pain does not become more frequent or severe over time.
Unstable angina is chest pain that is sudden and gets increasingly worse. The chest pain:
Occurs without cause (for example, it wakes you up from sleep) Lasts longer than 15 - 20 minutes Responds poorly to a medicine called nitroglycerin May occur along with a drop in blood pressure or significant shortness of breath People with unstable angina are at increased risk of having a heart attack.
Coronary artery spasm is a rare cause of angina.